Migrate to Azure Functions isolated worker model (.NET 8+ support & in-process deprecation) #78
Description
The current implementation of fhir-loader uses the in-process Azure Functions model, which is now deprecated and scheduled for complete sunset by November 2026. In-process is also not supported for .NET 8+ without using the temporary "FUNCTIONS_INPROC_NET8_ENABLED" workaround. This creates technical risk for projects adopting newer .NET runtimes.
Please migrate the project to use the Azure Functions isolated worker model, which is now the recommended architecture
• Improved DI, middleware support, logging
• Full alignment with Azure Functions roadmap